
where we first employed the triangle inequality, then a trace inverse estimate to pass from the face \(F\)  to the neighboring elements \(T_1\)  and \(T_2\)  [1]}, and finally another inverse estimate to arrive at a bound in terms of \(\nabla v_h\)  [2]}. Using the same inverse estimate it follows that
\(h^2 \Vert  v_h \Vert ^2_{s_h} \lesssim h^2 \Vert  \nabla v_h \Vert ^2_{\Omega _h} \lesssim \Vert  v_h \Vert ^2_{\Omega _h}\) 
